Cryptographic system and apparatus



Dec. 16, 1952 A. R. MURRAY 2,621,424 CRYPTOGRAPHIC SYSTEM AND APPARATUS Filed May 2, 1947 INVENTOR am. W 3

Patented Dec. 16, 1952 UNITED STATES PATENT OFFICE oRYrroeRArnIc SYSTEM AND APPARATUS k R. Murray, Arlington, Va. I v I Application May 2, 1947, s r al No. 745,474

This invention relates broadly to the art of cryptography and in its more specific aspects it relates to a new cryptographic system "or cipher for coding and decoding messages and the like and apparatus for effecting the coding and decoding of messages and the are according to's'uch cipher and other ciphers; and thenature and objects of the inventionwill be readily recognized and understood by those skilled in the arts to which it relates in the light of the following explanation and detailed description of the accompanying drawings'illustrating what I at present believe to be the preferred embodiments and mechanical expressions of the invention from among various other forms, arrangements, combinations and constructions, of which the invention is capable within the spirit and scope thereof.

Broadly speaking, thereare two types of cryptographic systems or ciphers in use for thetransmission of secret messages. One is the transposition cipher, in which the alphabetical letters of a message are transposed with one another according to a predetermined design or pattern or series of such designs or patterns, which are known to the sender and receiver in advance. The other is the substitution cipher, in which other letters are substituted for the letters of a message, following a pattern or system of substitution known to the sender and receiver in advance.

The simplest form of substitution cipher is one in which each letter of the'alphabet is arbitrarily represented by one other letter, such as the next succeeding letter in the ordinary alphabetical order. In such a cipher, A would be represented by B, B by C, C by D, and so on. A message of this character is extremely easy for almost anyone to decipher with a little study, and cryptographers have developed numerous substitution patterns and systems of greatly increased complexity, the chief feature of which is the representation of an alphabetical letter by any of a number of other letters, instead of by just one, and such systems are in common use throughout the world.

One way that some systems achieve the representation of a letter by any of a number of others is by the use of Whatis termed'a key, which is a combination of letters equal in numberto the letters of a message. The key is in the possession of both the sender and receiverbefore the message is sent. In enciphering or coding a message, the sender begins by juxtaposing the first letter of his message with the first letter of the key, and the key letter determines what the alphabetical symbolwill be for the messag l'etter.

4 Claims. (01. 25 3) 2 Thus, if the message letter is A and the key letter isM, then the cipherletter'will be Xor whatever other letter has been'decided upon in advance to represent such a combination. But if the key letter is R,'then the'cipher letter is something else, depending What the advance formula is for the combination of A and R. The same procedure is followed for the balanceof the message.

The key, as has been said, is" in the possession of both the sender and receiver. It may' be a word or sentence or a long series of Words, repeated over and over again to match the message in length. But' to achieve the utmost secrecy, it is necessary for the key to be a patternless series of letters, chosenat random, and never repeated. This prevents therepetitions which enable'cryptographers to decipher or break messages. If such a key is used,- there is no known way by which a message can be deciphered without a knowledge of the individual key used;

The receiver of a message prepared by such a cipher follows a similar procedure to that of the sender. Having the key already in his possession, he juxtaposesthe first letter of it with the first letter of the cipher message. If the first letter of the cipher message is X, and the first key letter is M, he then follow whatever formula has been decided upon to determine what message letter is represented by the combination of); and 'M. He proceeds in the same way until the entire message has been decoded.

I have devised a cryptographic system or cipher which follows the same basic principles just described and others in the art of cryptography, but which differs in several important respects from substitution ciphers now in use. It achieves the same secrecy and unbreakability possessed by the most secret and complex formulas in use, and produces equal and perhaps superior results to those produced by automatic machines which scramble and unscramble message through electrical impulses. Its messages in cipher have every advantage of those of the most advanced substitution ciphers, including the following three:

1. Each alphabetical letter of a message can be representedby any of the 26 letters of the alphabet.

2. No repetitive patterns or routine sequences appear which might enable the messages to be broken.

3; Coding and decoding can be done manually with rapidity; and the cipher also lends itself to semi-automatic and automatic use with apparatus.'

One of the major differences between my crypgame.

tographic system and others is the use in y system of the extremely simple mathematical coding and decoding formula of my invention, which makes unnecessary the employment of complex and arbitrary patterns and designs. Moreover, it is unnecessary to preserve secrecy as to the coding and decoding formula, as knowledge of it does not enable anyone to decipher messages without knowledge of the individual key being used.

My cryptographic system in its broadest terms involves a mathematical system wherein multiple numerical values are assigned to the letters of the alphabet, and coding and decoding are accomplished by simple addition or subtraction of these numerical values. A key, as described above, is used and is in the possession of both the sender and the receiver of a message.

It is therefore a primary object of my invention to provide a system of cryptography which substitutes other letters of the alphabet for those of a message to provide a cipher message.

It is also an object of my invention to provide a system of cryptography wherein a letter of a message may be represented in cipher by any of the 26 letters of the alphabet.

It is another object of my invention to provide a system of cryptography wherein coding and decoding are based on the relative numerical values assigned to the letters of the key and the message and the key and the cipher message.

Another object of my invention is to provide a system of cryptography wherein each letter of the a routine of any character whatsoever.

Itis a further purpose and object of my invention to provide a system of cryptography in whichthe key for any message unit may comprise any of the letters of the alphabet which are chosen at random. V

This invention has also been devised to provide a system of cryptography whose cipher messages cannot be deciphered or broken, even though the operation of the system is known, unless the particular key which is being used at the time is known.

It is also a characteristic of this invention to provide a cryptographic system which may be operated simply, which does not employ complex and arbitrary patterns, designs and letter-groupings, and whose operation does not require the memorizing of symbols or anything more than normal mental ability.

It is another characteristic of this invention to provide a system of cryptography which may be operated by any person acquainted with the alphabet and who is able to do simple addition and subtraction.

And yet another purpose of my invention is to provide a system of cryptography which can be operated efficiently and speedily without the use of charts, tables, guide-lists, devices or apparatus of any kind.

Another purpose of my invention is to provide a system of cryptography which can be operated efficiently and speedily by the use of semi-automatic and automatic coding and decoding apof important messages which must be maintained in secrecy.

Anotherobject of this invention is to provide a secretcode or cipher system which may be used by children as a toy or game.

In order to increase the convenience and speed of operation of the system and to reduce the possibility of errors, I have devised devices or apparatuswhereby messages may be coded and decoded with facility and with a minimum quantity of mental effort.

The devices which I propose to use in coding and decoding messages in accordance with the fundamental precepts of my cryptographic system are simple and attractive to use and have been devisedto add interest to the transmission of secret or decoded messages.

Another feature of the devices I have devised for coding and decoding messages in accordance with my system, resides in a simple manipulation thereof to produce visually the coded or decoded message.

The devices for coding and decoding messages have been designed for use by children as well as by adults and greatly simplify the operation and the application of the systemin actual use in the sending andreceiving of coded messages.

Another object of my invention is to provide mechanical devices for coding and decoding messages which are simple and economical to manufacture while being sturdy and long lasting under actual use conditions. I

With the foregoing general objects, features and results in view, as well as certain others which will be apparent from the followingexplanation, the invention consists in certain novel features and designs, construction, mounting and combination of elements as will be more fully and.

Fig. 4 is a view in longitudinal vertical section V through the device illustrated in Fig. 1 of the drawings.

Fig. 5 is a plan view of the coding and decoding cylinder of the coding and decoding device, the cylinder being illustrated in flattened form.

The cryptographic system which I have invented. is primarily basedon substituting for each letter of a message another alphabetical letter. The core of the system is the manner of selection of the substitute letters. As has been described above, in my system a key is used, consisting of a series of letters of the same length as the letters of the message, and the key is in the possession of both the sender and the receiver. The key may consist of the same letter repeated over and over again, of a single word repeated over and over again, or of a phrase or sentence or longer'passage, but for the purpose of utmost secrecy it should be a series of letters selected at random and should not be used for more than one message, so that no patterns and repetitions are formed.

The successive letters of the key determine what the substitute letters will be for the original letters of the message. Thus, if the first letter of a message is A, the substitute for it is determined by the first letter of the key, which may be any one of the 26 letters of the alphabet, and therefore the substitute letter may be any one of the 26 letters of the alphabet, including A. As numerical values are assigned to the various letters of the alphabet, what is actually done by the sender is to add the first message letter to the first key letter as if they were both figures, and their sum becomes the substitute or cipher letter. When the receiver receives this cipher letter, he is already in possession of part of the sum, which is the key letter used. By simply subtracting this from the cipher letter, he knows what the original message letter was.

The receiver of the coded letter may also determine what the original message letter was by adding the complementary numerical value of the key letter to the numerical value of the cipher letter, the complementary numerical value being determined by a mathematical system based on units of 26 instead of units of 10, as in the decimal system. This is explained fully below.

The niunerical values assigned. to each alphabetical letter range from 0 to 51. Each letter is assigned two numerical values, twenty-six numbers apart. Any letters may be selected for the different sets of numerical values, but for convenience I use in this specification the numerical values ordinarily associated with the letters of the English alphabet. Thus, A will be represented by 1 and 27, B by 2 and 28, C by 3 and 29, and so on. Z will be represented by 0 and 26.

To explain the operation of this system, it is necessary to point out that there are three dis- DGKQOSBWXADILPBDDZLNRNCEHQLR.

tinct elements involved which concern both the sender and receiver of a message. The first is the message in its original form. This will hereafter be called the message, and each letter of it will be called a message letter. The second is the enciphered or coded message which is transmitted. This will hereafter be called the coded message and each letter of it will be called a code letter. The third is the key, and will be so called, and each letter of it will be called a key letter.

The sender of a message begins by juxtaposing the first letter of the message with the first key letter, just as if he were adding two numbers. Let us assume that these two juxtaposed letters i t if 8 are-F and J. The numerical value of these two letters are 6 and 10. Adding them together brings a. total of 16, which is the numerical value of the letter P. The code letter therefore is P. It will be observed that the sender uses thelower numerical value of'each letter in his addition. The total, however, maybe a figure representing the higher numerical value of some other letter. To illustrate, the numerical values of H and U are 8 and 21. If these happen to be juxtaposed, one as a message letter and the other as a key letter,

the sum of the twoamounts to 29, which is the higher numerical value of the letter C, and therefore C is the code letter. The sender proceeds with each combination of a message letter and a key letter, and when finished, sends to the receiver the coded message.

The receiver then proceeds to subtract the key letters from the code letters he has received. Thus, if the first code letter is T and the first key letter is B, he subtracts the numerical value of B, which is 2, from the numerical value of T, which is 20, and his result is 18 or R. It will be observed that the receiver has used the lower numerical value of each letter. Sometimes, however, the lower numerical value of the code letter is less than the lower numerical value of the ke letter. For example, the code letter may be D, whose lower numerical value is 4, and the key letter may be L, whose lower numerical value is 12. As it is impossible to subtract 12 from 4 without a minus result, the receiver assigns the higher numerical value to D, which is 30, and the result of the subtraction of 12 from 30 is eighteen, the numerical value of R. Thus he knows that R is the message letter.

As has been said above, the receiver may achieve the same result by the use of addition instead of subtraction. To do this, he adds to the lower numerical value of the code letter the complementary numerical value of the key letter. This complementary value is always the difference between the numerical value and 26. Thus, if the first code letter is T and the first key letter is B, he adds to the numerical value of T, which is 20, the complementary numerical value of B, which is 24, and the result is 44 or the higher numerical value of R.

As an example of the operation of my cryptographic system, let us code an actual message for transmission. We shall assume that the follow"- ing is the key in the possession of both the sender and the receiver:

Let us assume that the message to be trans mitted is:

PEACE TREATY SIGNED.

The conventional method of preparing cipher messages for transmission is to arrange them in.

PEACE XTREA TYXSI GNEDQ Q The sender would arrange and group the message and the key in the following manner:

SBWXA DILPB DDZLNI R XTREA TYXS I GNEDQ Q It will be noted that the key, being longer than the message, is not used in its entirety.

The next step would be to determine the numerioal values of the various letters comprising both the key and the message, and by addition thereof, the values of the code letters would be ascertained. The following illustrates how the code message is determined.

Following the arrangement and grouping of '(1), the numerical valuesof the letters are as follows in (2) l9 -2 23 24 l 4 9 l2 l6 2 4 4 0 12 14 18 '24 20 18 5 1 20 25 24 19 9 7 14 5 17 17 QVOOBXHIIKKR EP EI ,Thus, the sum of numerical values of D and .P is ;20,which is the numerical value of T. G

andE added together are 12 or L, and so on.

Thus, the cipher or code for PEACE TREATY SIGNED, using the key letters selected above will be:

TL LTY QVOCB XHJIK KRE'PE I Continuing with the message, let us now decode the cipher or coded message that is transmitted'to the receiver. The receiver should arrange the code with the key letters, which were previously in his possession, as follows:

TL'LTY gvoce XHJIK K GKQO BWXADILPBD He would then determine the numerical values of the letters as follows, subtracting the value of each key letter from the value of each code letter:

(Message) P E A C E A T Y X PEAOEXTREA'TYXSIG It should be noted how my system makes possible the use of any of the twenty-six letters as a code letter for a message letter. In the example of the message, Peace Treaty Signed, the letter E appears four times, but in each case is represented by a different code letter: L, Y, C and E. Also, the key message contains several letters used more than once, but in each case they represent entirely different message letters.

In the accompanying drawings, I have illustrated a device whereby messages may be coded and coded messages may be decoded with great facility. This device for automatically coding and decoding is based upon the fundamental principle of the cryptographic system which I have outlined hereinabove. This device has been designed with the purpose of greatly simplifying the actual coding and decoding operation so that messages may be coded, and coded messages decoded by children who know the letters of the alphabet, as well as by adults.

In the drawings, I have illustrated a coding and decoding device which is easily operable and pleasing and attractive in appearance. This device comprises an inner cylindrical member which for purposes of descriptive clarity, I shall term the coding and decoding cylinder, and I have designated this cylinder in its entirety by the numeral I. This cylinder may be fabricated of plastic, wood or of any other suitable material. I provide an inner tubular element 3, formed of plastic or other suitable material, of substantially less diameter than that of the coding and decoding cylinder I, the tubular element -3 is adapted to extend into the coding and decoding. cylinder and is adapted to project beyond the end of the coding and decoding cylinder to provide a handle 5. The coding and decoding cylinder on the outer end thereof may be provided with an inner extending annular flange I, for fastening, in any suitable manner as at -9 to the inner tubular element 3. The coding and decoding device of my invention also includes what I shall term a controlling sleeve of plastic, wood or other suitable material which sleeve, I shall designate in its entirely by the numeral I I. The sleeve I I being mounted by means of an inner E P E I extending annular flange I3, on an inner tubular member I5, which may likewise be made of plastic or other suitable material, and is of substantially less diameter than that of the controlling i 2 it i1 i2 9 7 E E 1 '1? E 1 G N E D Q o sleeve. The inner tubular element I5 projects ranged within the controlling sleeve, the inner tubular element I5 adapted to telescope within the open inner end of the inner tubular element 3, as at 2i. It will thus be appreciated that the cylinder and sleeve having the tubular elements are telescopically arranged when in operative position and the sleeve and cylinder as well as the inner tubular elements are relatively rotatable for a purpose to be hereinafter described.

Consideration particularly of Fig. 2 of the drawings, wherein the various elements which have been hereinbefore described are illustrated in operative relative positions, discloses that the open end 23 of the controlling sleeve II is spaced from the handled end of the coding and decoding cylinder I. In order to limit the telescoping movement of the controlling sleeve upon the cylinder so as to leave an open area between the handled end of the cylinder and the open end 23 of the sleeve, I may provide the inner tubular element 3 with an internal bead or the like stop means 25 for limiting engagement with the inner end of the inner tubular element I5. Any other convenient and desirable stop means may be utilized to properly axially locate sleeve II relative to cylinder I.

The particular construction and mounting of the coding and decoding cylinder and the controlling sleeve on the inner tubular elements which form the handles is illustrated in the drawings merelyby way of example and not by way of limitation, as it is to be distinctly understood that a coding and decoding device functioning in accordance with the precepts of this invention may take various structural forms other than that shown in the drawings and still fall completely within the spirit and scope of my invention. Any mounting arrangement for an assembly comprising a coding and decoding cylinder and a relatively rotatable telescopic controlling sleeve therefor is within the pirit of my invention.

n the end of the coding and decoding cylinder l, which projects beyond the end 23 of the controlling sleeve II, I provide the alphabet as disclosed at 21 in Figs. 1 and 5. The letters of the alphabet 21 may be printed, stamped, embossed or placed on the projecting end of the coding and decoding cylinder in any desirable manner, and this alphabet ring I shall hereafter term for descriptive purposes, the primary alphabetical ring of the coding and decoding cylinder.

In Fig. of the drawings, I have disclosed the coding and decoding cylinder with the various indicia thereon which I am about to describe, including the primary alphabetical ring 21, the cylinder being flattened for illustrative purposes only. Referring particularly to Fig. 5 of the drawings, it will be appreciated that I have printed, stamped or otherwise impressed upon the surface of the coding and decoding cylinder l a plurality of alphabetical series, and I shall designate this entire coding and decoding system of alphabetical series on the coding and decoding cylinder by the numeral 29. This entire coding and decoding alphabetical system is axially spaced from the primary alphabetical ring '21 by a blank space or a blank ring 31.

The alpabet system 29 includes a circumferential (vertical in Fig. 5 of the drawings), alphabetical ring 33 which I shall term the base coding ring. The alphabetical ring 33 is the first alphabetical ring axially adjacent to the blank space 31. At the opposite end of the alphabetical system 29, I print or otherwise provide a further circumferential (vertical in Fig. 5 of the drawings), alphabetical ring 35 which I shall term the base decoding alphabetical ring. I have thus provided an alphabetical ring at each axial end of the alphabetical system 29. Between each letter of each alphabetical ring 33 and 35, I print or otherwise form on the coding and decoding cylinder in the area 29 thereof axial alphabetical lines 31, thus on the first such alphabetical line referring to Fig. 5 of the drawings, the line starts with the letter A and runs through the alphabet and ends with the letter A the first letter of the circumferential alphabetical ring 35. The second alphabetical line starts with B the second letter of the circumferential alphabetical ring 33 and goes through the alphabet ending with the letter B, the second letter of the circumferential alphabetical ring 35. This progressive arrangement of the alphabet system within the area 29 is followed, and thus an axial alphabetical line is provided for each letter of the alphabet, each line commencing with the letter in the circumferential alphabetical ring 33 and ending with the same letter in the circumferential ring 35. Obviously, since the area 29 between rings 33 and 35 is filled with the axial alphabetical lines 31 there will of course be in this area a plurality of circumferential alphabetical rings 38, of twenty-six letters each. Also since each axial alphabetical line 37 starts and ends with the same letter, each axial line 31 will include twentyseven letters, and clearly there will be twenty- 10 seven circumferential rings including rings 33 and 35.

It is the purpose of this device to eliminate the mental calculations which are necessary in coding and decoding under this system as outlined above, and the devices illustrated in the drawings function automatically upon certain manipulations thereof by the user to disclose to the users view, the coded letter or the message letter, when the elements of the device are arranged in proper relative positions according to the key letter and the message letter or the coded letter and the key letter.

The controlling sleeve is rotatable relative to the coding and decoding cylinder and envelopes the alphabet system 29 which is provided on the body of the coding and decoding cylinder. Fig. 3 of the drawings illustrates the controlling sleeve of my invention in flattened form and it will be observed that I have provided a diagonally disposed series of coding and decoding apertures 99 which are out into the material of the controlling sleeve ll, so that upon rolling the flattened material of the controlling sleeve into tubular form, the series of coding and decoding apertures 99 will be helically arranged about the controlling sleeve as particularly shown in Fig. 1 of the drawings. It will thus be appreciated that in the instant type of apparatus, I use only one series of apertures 01' windows, and these are used in both the coding and the decoding operation.

On the end of the controlling sleeve II, which in operative position is adapted to be adjacent to the alphabet ring 21, I print or otherwise provide thereon, a coding alphabet ring Illl and a decoding alphabet ring [03, and I preferably form an annular bead I05 at or adjacent to the open end of the controlling sleeve II, and I form a further annular bead I01 inwardly spaced from the bead I05 and formed in the controlling sleeve inwardly adjacent relative to the decoding alphabet ring I03.

As will be hereinafter explained, in a coding operation, the coding alphabet ring It)! is used in conjunction with the primary alphabet ring 21, while in a decoding operation, the decoding alphabet ring I03 is used in conjunction with the primary alphabet ring '21. I have provided means to facilitate use of this device in the coding and decoding operations so as to eliminate the possible use of the wrong alphabet ring in conjunction with the pr-imaryalphabet ring 21 in a coding or decoding operation. In order to cover or block out the decoding ring H13 in a coding operation, and the coding ring [iii in a decoding operation, I have provided a slip ring I09 which is adapted for axial sliding operative movement on the controlling sleeve confined thereon between the beads I05 and IN. In Fig. 1 of the drawings, I have illustrated the device in operative coding position with the ring I09 in position blocking out the decoding ring I03, while in Fig. 2 of the drawings, I have illustrated the device in operative position for a decoding operation, the slip ring I89 having been axially moved from position covering the decoding ring Hi3 into position covering the coding ring Ifll. It will be understood that the beads 35 and I0? maintain the slip ring within the area of the coding and decoding rings IE3! and E83 and facilitate the operation thereof.

In using this device in a coding operation, the various elements thereof will be disposed generally in accordance with the disclosure of Fig. l

of the drawings. Assuming that the letter A is the key letter, and the letter A is the message letter, the slip ring I09 is disposed in position covering the decoding ring I03 whereupon the controlling sleeve is rotated relative to the coding and decoding sleeve until the letter A in the coding alphabet ring It] is disposed in alignment or juxtaposed relative to the letter A of the primary alphabet ring 21. The operator of the device then locates whichever aperture of the series of apertures 99 is in alignment with the juxtaposed letters A, and the letter on the alphabet system 29 which is visible through such aligned aperture will indicate to the operator the code message letter, in this case the letter B. Since the alphabetical numerical values of the letters A of the key and message letters is 1, the sum thereof being 2, the alphabetical numerical value of the letter B, the code letter visible in the aperture is B.

The device as illustrated in Fig. 2 of the drawings is in operative decoding position, the slip ring 109 being disposed in position covering or blocking out the coding alphabet ring l]. Assuming that the letter A is the coded message letter, and the letter Y is the key letter, the operator of the device rotates the controlling sleeve relative to the coding and decoding cylinder until the key letter Y on the decoding alphabet ring is in alignment with or juxtaposed relative to the letter A, that is, the coded message letter on the primary alphabet ring 27 is in alignment therewith. The operator then locates the aperture in the series of apertures 99 which is in alignment with the letters A and Y on the primary alphabet ring and the decoding alphabet ring respectively, and the letter visible through the aperture will constitute the message letter.

It will thus be evident that I have provided a particularly effective device for coding and decoding. This device will eliminate to a great extent, the possibility of errors by the user thereof, in making use of the wrong alphabet ring on the controlling sleeve in a particular operation.

Thus, it will be seen that the series of windows 99 serve as both coding and decoding windows, and that they perform either an adding or subtracting operation, depending on whether the coding alphabet ring or the decoding alphabet ring is used. It will also be seen that the procedure for coding and decoding is the same, except that in coding, the desired letters on the primary alphabetical ring 27 are juxtaposed with the desired letters on the coding alphabetic ring; and that in decoding, the desired letters on the primary alphabetical ring 27 are juxtaposed instead with the desired letters of the decoding alphabetic ring.

The manner in which the series of windows 99, perform an adding operation in coding has been described in connection with the device of Figures 1 through 5 of the drawings.

The reason that the same series of windows 99 perform a subtracting operation when the decoding alphabetic ring is substituted for the coding alphabetic ring lies in the arrangement of alphabetical letters in the former. This arrangement uses a variation of the mathematical procedure known as substraction by addition of complementary numbers, which I have adapted for use with my crytographic system, using units of 26 instead of the conventional units of in the decimal system.

In my system of cryptography, each letter of the alphabet is assigned two numerical values, 26f

numbers apart, as has been previously explained. For this reason, the result of subtracting the numerical value of one letter from another can be reached either by direct subtraction of the subtrahend, or by the addition of the complementary number of the subtrahend. The complementary number of the subtrahend is always the difierence between it and 26. Thus, the complementary number of 12 is 14. To illustrate, if a decoding operation is undertaken by my cryptographic system, and if the numerical values of the letters of the alphabet have been assigned in the manner used in this specification, the figure 12 represents the lower numerical value of the letter L. Assuming that ,this is the key letter, and that R is the code letter, we subtract L or 12 from R or 18, reaching a result of F or 6, which is the message letter. But the same result can be reached by adding the complementary number of L, which is 14, to R or 18. In doing this, the result is 32, which is the higher numerical value of F, and therefore the result is the same as by direct subtr-ac tion.

The deco-ding alphabetic ring has an arrangement of letters in which each letter is aligned axially with the window in the series of windows 99 which represents its complementary numerical value. Thus, the letter B appears in a position in which it is aligned axially with the window which represents an addition of 24, because B has a numerical value of 2 and itscomplementary number is 24. The window which represents an addition of 24 is the window that in coding is aligned with the letter X in the coding alphabetic ring.

The entire arrangement of letters on the decoding alphabetic ring, in accordance with this principle, is that of a reverse alphabet in which the letters of the coding alphabetic ring and of the decoding alphabetic ring adjacent to and parallel with each other are as follows: AY, B--X, C'W, DV, E-U, FT, G-S, H'R, IQ, J-P, K--O, LN, MM, N-L, 0-K, PJ, QI, RH, SG, TF, U-E, VD, WC, X-'B, Y-A, ZZ. This arrangement applies to the numerical values assigned to-the various letters in this specification, and would differ if different numerical values were assigned to the various letters of the alphabet, but the principle would be the same.

I claimi 1. A coding and decoding device, including a coding and decoding cylinder having a primary alphabet ring thereon visible from the exterior of the device, and provided with an alphabetical system thereon, and a controlling sleeve in 0perative position telescopically mounted on and enveloping that portion of the coding and decodiing cylinder having the alphabetical system thereon, the controlling sleeve being relatively rotatable with respect to the coding and decod+ ing cylinder, the controlling sleeve having a series of apertures in that portion thereof disposed about the alphabetical system on the coding and decoding cylinder, and a coding alphabet ring and a decoding alphabet ring fixed on the controlling sleeve adjacent the end thereof which is disposed adjacent the primary alphabet ring, the coding and decoding alphabet rings being rotatable with the controlling sleeve, the coding alphabet ring adaptable for use with the primary alphabet ring in a coding operation and the de: coding alphabet ring adapted for use with the primary alphabet ring in a decoding operation,

the aperture of the series of apertures which is in axial alignment with a selected letter in the primary alphabet ring and either the coding or decoding alphabet ring uncovering a desired letter, and movable means carried on said controlling sleeve for covering the decoding alphabet ring in a coding operation and for covering the coding alphabet ring in a decoding operation.

2. A coding and decoding device, including a coding and decoding member having a primary alphabet thereon visible from the exterior of the device, and provided with an alphabetical system thereon, and a controlling element in operative position rotatably associated with said cooling and decoding member and covering that portion thereof having the alphabetical system thereon, the controlling element having a series of apertures in that portion thereof covering the alphabetical system on the coding and decoding member, and a coding alphabet and a decoding alphabet fixed on said controlling element adjacent to said primary alphabet and rotatable with said controlling element, the coding alphabet adaptable for use with the primary alphabet in a coding operation and the decoding alphabet adapted for use with the primary alphabet in a decoding operation, the aperture of the series of apertures which is in axial alignment with a selected letter in the primary alphabet and a letter in either the coding or decoding alphabet uncovering a desired letter on the alphabetical system, and movable means carried on said controlling element for covering the decoding alphabet in a coding operation and for covering the coding alphabet in the decoding operation.

3. A coding and decoding device, including a coding and decoding cylinder having a primary alphabet ring thereon visible from the exterior of the device, and provided with an alphabetical system thereon, and a controlling sleeve in operative position telescopically mounted on and enveloping that portion of the coding and decoding cylinder having the alphabetical system thereon, the controlling sleeve being relatively rotatable with respect to the coding and decoding cylinder, the controlling sleeve having a series of apertures in that portion thereof disposed about the alphabetical system on the coding and decoding cylinder, and a coding alphabet ring and a decoding alphabet ring fixed on the controlling sleeve adjacent the end thereof which is disposed adjacent the primary alphabet ring, the coding and decoding alphabet rings being rotatable with the controlling sleeve, the coding alphabet ring adaptable for use with the primary alphabet ring axial movement to position covering the decoding alphabet ring in a coding operation and for covering the coding alphabet ring in a decoding operation.

4. A coding and decoding device, including a coding and a decoding cylinder having a primary alphabet ring thereon visible from the exterior of the device, and provided with an alphabetical system thereon, and a controlling sleeve in operative position telescopically mounted on and enveloping that portion of the coding and decoding cylinder having the alphabetical system thereon, the controlling sleeve being relatively rotatable with respect to the coding and decoding cylinder, the controlling sleeve having a series of apertures in that portion thereof disposed about the alphabetical system on the coding and decoding cylinder, and a coding alphabet ring and a decoding alphabet ring fixed on the controlling, sleeve adjacent the end thereof which is disposed adjacent the primary alphabet ring, the coding and decoding alphabet rings being rotatable with the controlling sleeve, the coding alphabet ring adaptable for use with the primary alphabet ring in a coding operation and the decoding alphabet ring adapted for use with the primary alphabet ring in a decoding operation, the aperture of the series of apertures which is in axial alignment with a selected letter in the primary alphabet ring and a letter in either the coding or decoding alphabet ring uncovering a desired letter in the alphabetical system, and a slip ring carried on said controlling sleeve for axial movement to position covering the decoding alphabet ring in a coding operation and for covering the coding alphabet ring in a decoding operation, and means limiting the axial movement of said slip ring, said means being disposed on said controlling sleeve at the side of the coding and decoding alphabet ring.

ALAN R. MURRAY.

REFERENCES CITED The following references are of record in the nle of this patent:

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